I have concluded and believe that 1/3 of the applicant pool applies early (May - August) and gets an offer of acceptance for 2/3 of the class seats by December. That leaves 2/3 of the applicant pool (i.e. January MCAT takers, MD applicants who haven't been accepted and other late applicants for a host of reasons) scrambling for an acceptance in 1/3 of the total seats that may be remaining as yet unfilled.
Schools are allowed to accept a small percentage over their class size in anticipation of the applicant not showing up or declining at the last moment. At my interview at Wilkliam Carey U., I ws told that 108 would be accepted for a class of 100.
Large class deposits are due on April 15th. Seats open when applicants with multiple acceptances have to make a firm, final decision. So, the lesson is that by January classes may not be full but they are 60 -70% full and many applicants are competing. Required statistics rise. The competition gets tougher. One take away or lesson is apply early.